Sixty per cent of Britons want the UK military to withdraw from or reduce its presence in Afghanistan, according to an international poll released today which showed that the British are the most hostile in western Europe to their troops' presence in Afghanistan.

A separate British survey showed that a similar figure believed UK troops should never have been deployed in Afghanistan or Iraq. The survey of opinion in 13 countries conducted annually by the German Marshall Fund of the United States found that 41% of Britons wanted troops pulled out of Afghanistan while a further 19% wanted a reduction in troop numbers. All 13 countries polled, including the US, have troops in Afghanistan. The British hostility to the presence there was almost matched by Germany and exceeded in the EU only by Poland, Bulgaria and Romania, according to the Transatlantic Trends survey.

In a week that has seen the Afghan war intrude for the first time into Germany's election campaign because of the civilian casualties from a German-ordered air strike, three out of four Germans did not believe the western effort would stabilise Afghanistan. Four out of five polled across Europe rejected Barack Obama's pleas for greater troop contributions from Nato allies in Europe for Afghanistan.

The survey's results, contrasting British and European gloom on Afghanistan with a more optimistic and interventionist attitude from the Americans, came in the middle of a worsening crisis that prompted Gordon Brown, Chancellor Angela Merkel of Germany, and President Nicolas Sarkozy of France to issue a joint call for a major international conference by the end of the year.

In a letter to Ban Ki-moon, the UN secretary general, the European leaders hinted at drafting plans for a partial retreat. They called for agreement on "new benchmarks and timelines" and "to set our expectations of ownership and the clear view to hand over responsibility step by step to the Afghans, wherever possible".

In a separate British poll by the National Army Museum on attitudes towards the armed forces, 53% of those questioned disagreed with the decision to deploy British troops to Afghanistan, while 25% said they agreed..

The Tory leader, David Cameron, has meanwhile apparently cast doubt on the Afghanistan elections, blaming "naked" irregularities in the poll.

In private remarks picked up by a BBC camera crew, he was heard to say that disparities between the number of votes cast and the number of people who voted "could not be right". The comments, made to shadow foreign secretary William Hague, are likely to be interpreted as opening a further gulf between himself and the prime minister on the elections.

Cameron was recorded as saying yesterday: "The things that seem to have happened are so naked … you just saw the number of votes and the number of people who actually turned up at polling stations. It just could not possibly be right."